Suggestions of steps that people can take to reduce their carbon footprint generally focus on the home (turn down the thermostat) and transportation (drive less). Only occasionally is there an article that looks at the relationship between landscaping decisions and the changing climate. And yet in significant ways, gardens both contribute to, and are affected by, climate change.
Evanston gardeners have begun to notice that plants are leafing and blooming earlier — warning signs that the climate is already changing. While warmer, shorter winters may sound like a good thing for gardens, the potential benefits from a longer growing season will be eclipsed by other problems: more heat waves, periods of drought, and damaging storms as well as the proliferation of garden weeds, invasive species, insect pests, and plant diseases.
A Conventional Garden’s Footprint
Although plants absorb carbon dioxide (CO2) during photosynthesis, conventional gardens are significant sources of this greenhouse gas (GHG). The gasoline-powered equipment marshaled to maintain lawns and tidy up walkways generates large amounts of CO2 as well as ozone-forming pollution.
The fertilizers and pesticides applied to conventional gardens account for still more energy consumption and GHG emissions. The manufacture of synthetic fertilizers is very energy intensive, and both synthetic and organic fertilizers release nitrous oxide, a powerful GHG. Moreover, heavy rains can wash fertilizers and pesticides into the sewer system.
Climate Challenges for Evanston Gardens
In the coming years, Evanston is projected to experience
• more extremely hot days,
• more heavy downpours,
• wetter winters, springs, and falls, and
• drier summers and more frequent short-term droughts.
These climate changes will have a significant impact on area gardens. Some plants and trees that have done well here in the past will no longer thrive in the warmer conditions. Some will fail because the winter cold period is not long enough; others will be vulnerable to hotter, drier summer weather.
Warmer temperatures will benefit weed growth and allow the northward spread of invasive plants. Dandelions, ragweed, and garlic mustard will thrive. Milder winters will allow insect pests to survive the cold season that normally limits their numbers. And longer warm seasons will allow some pests to produce more generations per year.
Creating More Sustainable Gardens
There are many things that Evanstonians can do, however, both to lessen the climate impact of their gardens and to help their gardens adapt to the changing conditions that lie ahead.
Limit lawn area. Replacing a section of turf grass with ground cover and/or native plants will reduce the amount of fossil-fuel intensive maintenance needed for lawn care. It will mean less mowing, watering, and fertilizing and will provide valuable habitat for wildlife. It will also improve stormwater management as it will replace shallow-rooted turf grass with deeper-rooted adapted plants.
For those areas where lawn is desired, the climate-sensitive choice will be a low-maintenance, drought-resistant species of turf grass that recovers well after drought conditions.
Choose the right plant for Evanston’s changing climate. Pick plants that resist pests and need less water. Incorporating a diversity of native plants will help provide food for wildlife.
Be careful with fertilizers. Overuse of fertilizers can damage beneficial soil life and contaminate stormwater runoff. Replace synthetic fertilizers with compost and organic, slow-release fertilizers. Use just the amount needed and avoid applying it before a heavy rainstorm.
Practice smart watering. Mulching helps conserve water, stabilizes soil temperatures, prevents weeds, and feeds the soil, thus reducing the need for fertilizers. Soaker hoses and drip irrigation systems are more efficient than sprinklers. Use rain barrels and cisterns to collect rainwater for use in the garden. Water plants deeply and then allow the soil to partially dry out between waterings. Be alert to increased watering needs of plants and trees during summer dry spells.
Avoid using pesticides. Start with prevention: build healthy soil with compost and mulch; select pest-resistant plants; and pull weeds before they go to seed. Choose the least toxic solution and avoid overuse.
Let the rain soak in. As the frequency and intensity of heavy rainstorms increase, managing stormwater runoff will become more and more important. One option is to create a raingarden, a slightly sunken area filled with water-tolerant native plants whose long roots enhance the infiltration of rainwater into the ground. A raingarden typically retains 30 percent more rainwater than conventional turf grass. Another way to keep stormwater from rushing into the sewer system is to use porous, rather than impervious, materials for walkways and other hard surfaces.